[CEF] Implement Load Sharing Algorithm Support in Terraform Provider

[ChristopherJHart]

This PR adds support for CEF load balancing and port-channel load balancing configuration in the terraform-provider-iosxe.

These improvements enhance the iosxe_system resource with comprehensive load balancing capabilities including IPv4 and IPv6 CEF load-sharing algorithm configuration with port-based hashing, and port-channel load balance algorithm selection.

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CLI Commands Supported

CEF Load-Sharing Algorithm Support

ip cef load-sharing algorithm include-ports source
ip cef load-sharing algorithm include-ports destination
ip cef load-sharing algorithm include-ports source destination
ipv6 cef load-sharing algorithm include-ports source
ipv6 cef load-sharing algorithm include-ports destination
ipv6 cef load-sharing algorithm include-ports source destination

Port-Channel Load Balance Support

port-channel load-balance <algorithm>

Supported algorithms include: src-dst-ip, src-dst-mac, src-ip, src-mac, dst-ip, dst-mac, src-dst-mixed-ip-port, and other platform-specific options.

Benefits:

• Enables fine-grained control over CEF load balancing behavior for both IPv4 and IPv6 traffic using Layer 4 port information in hash calculations
• Improves traffic distribution across ECMP paths by including source and destination ports in the load balancing algorithm
• Provides flexible port-channel load balancing algorithm configuration to optimize traffic distribution across port-channel member links
• Enhances network performance and utilization through intelligent hash-based load distribution that considers Layer 3 addresses and Layer 4 ports

Platform Compatibility:
These features have been validated against Catalyst 9300 switches running IOS-XE 17.12.5. The implementation uses the modern cef-v2 YANG model (Cisco-IOS-XE-cef) which is supported across Catalyst switch and router platforms.

Technical Implementation:

• Added Cisco-IOS-XE-cef YANG model to code generation pipeline
• Implemented proper namespace handling for augmented YANG containers
• Correctly mapped YANG empty type leaves to boolean Terraform attributes
• Fixed xpath patterns to follow RESTCONF JSON namespace conventions
• Ensured idempotent behavior for all new attributes